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Stephenson College DP 98 1
Design Patterns
by Derek Peacock
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Introduction
Designing OO software is hard Specific enough for current problem General enough for future requirements Experts reuse past design solutions Patterns of classes to solve specific design
problems
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What is a Pattern
A Pattern NameName A ProblemProblem (When to apply the pattern) The SolutionSolution (How to solve the problem)ConsequencesConsequences (Space, time, flexibility,
portability, extensibility)
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Design Patterns
Creational Creating objects
Structural composition of objects
Behavioural Interaction between objects
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Creational Patterns
Abstract Factory
Builder
Singleton
Interface for creating families of related objects
Create complex object from representation
Create a only one globally accessible object
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Structural Patterns
Composite Decorator Façade Proxy
Part-whole hierarchies Attach additional responsibilities Unified interface to subsystems Provide surrogate for object
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Behavioural Patterns
Chain Interpreter
Iterator Memento
Provide a message chain Interpret a language with
grammar Provide access to elements Capture objects internal states
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